Hot metal extrusion method



INVENTOR. SCA/EIL Meme/LL A.

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HOT METAL EXTRUSION METHOD Oct. 31, 1967 Original Filed May ll, 1962 uwy@ Oct. 31, 1967y M. A. Scl-IEN.

. HOT METAL EXTRUSION METHOD 2 sheets-sheet 2 Original Filed May ll,1962 INVENTOR ScHE/L MERR/LL A.

BY qndfus 92 std/Q Arron/evs United States Patent O New York Originalapplication May 11, 1962, Ser. No. 193,974, now 1965. Divided and PatentNo. 3,210,978, dated Oct. 12, this application Apr. 30, 1965, Ser. No.452,245

6 Claims. (Cl. 72-38) This invention relates to a hot metal extrusionmethod and apparatus and particuluarly to the fluid shielding andpurging of the extruded metal member.

This is a division of application Ser. No. 193,974, filed May l1, 1962,now Patent No. 3,210,978.

Wire or rod-like members may be formed by disposing a billet in a dieand forcing the billet out through a restricted opening. Metals such ascarbon and alloy steels, nickel alloys and some of the other carbonmetals can all be extruded into wire-like members to provide anyparticular cross sectional configuration desired.

In order to facilitate extrusion, it has been found desirable tolubricate the die surfaces normally in contact with the hot metal aswell as the surfaces of the extrusion cylinder. In the hot extrusion ofmetals utilizing certain lubricants, the extruded members tend to formcoatings which result from the penetration of the members by thevolatile constituents which are carried through the die with the wirebeing extruded therefrom. This is particularly true in the extrusion ofcarbon and carbon alloy steel billets.

The extruded member tends to develop a carbon rich coating adjacent itsexterior surface. This undesirable coating is formed when carbonaceousmaterials occurring in the extrusion lubricant are gasied by the highextrusion temperatures as the extruded metal leaves the die. At the hightemperatures attained as the metal leaves the die, the iron content ofthe metal is able to absorb quantities of carbon. A carbon-iron solutionis formed which initially contains quantities of austenite andcementite. As the carbon concentration increases quantities ofledeburite are formed. As the metal rapidly cools, a two phase solidsolution of austenite and cementite forms on the surface of the extrudedmember, and a quantity of brittle ledeburite fuses to this coating.

The brittle hardness of the high carbon coating, which is primarily dueto the presence of ledeburite prevents practical cold drawing of theextruded metal because of wire fracture and excessive wear on the dies.

The present invention is particularly directed to the provision of ameans and method of preventing carburization or similar reactions withthe surface of the extruded metal following its expulsion from the die.In accordance with the present invention, the extruded metal issupported by a guide tube as it is extruded from the die. Means areprovided to continuously ush the guide tube with a gaseous medium tocontinuously shield the extruded metal and to prevent the volatilecarbonaceous constituents occurring in the extrusion process fromestablishing a carburizing atmosphere adjacent the extruded metal.Applicant has found air to be a satisfactory and inexpensive gaseousmedium for preventing carburization of the extruded metal.

If desired, the guide tube may be heated to maint-ain the carburizingagents in a volatile state in order to facilitate the flushing anddriving oif of these agents by the gaseous medium.

The present invention provides a simple and inexpensive method andapparatus for eliminating or substantially reducing the carburization ofextruded metal members and the like.

The drawings furnished herewith illustrate the best ice mode presentlycontemplated for carrying out the invention.

FIGURE 1 is a side elevational View of extrusion apparatus incorporatinga guide tube constructed in accordance with the present invention;

FG. 2 is a fragmentary enlarged View of a runout assembly including theguide tube shown in FIGURE 1;

FIG. 3 is a top View of a portion of FIG. 2;

FIG. 4 is an enlarged longitudinal section of the guide tube shown inFIGURES 1-3; and

FIG. 5 is a vertical section taken on line 5 5 of FIG. 4.

Referring to the drawings and particularly to FIGURE 1, a hot metalextrusion apparatus is shown including a die assembly 1 having acylinder 2 defining a die cavity within which a hot metal billet 3 isdisposed for extrusion into a relatively small diameter wire 4 ofindefinite length and many times the length of the billet 3. A ram 5forms a part of the extrusion apparatus and is aligned with cylinder 2and is adapted to be moved into the cylinder 2 and force the hot billet3 outwardly through a small cylindrical die opening provided in a dienib 6. A runout tube assembly 7 is mounted adjacent the die 6 andsupports the hot extruded metal as it is ejected or forced from the dienib 6. A nal runout track 8 is provided extending outwardly adjacent theouter end of the runout tube assembly 7 to support the long extrudedWire 4.

The illustrated die assembly 1 does not form any par-ticular of thisinvention and may be of any suitable construction. The illustnated dieassembly 1 is therefore described only in sutlicient detail to fullyunderstand the presen-t invention which is particularly directed to therunout tube assembly 7.

Generally, the die assembly 1 includes a support structure 9 for thecylinder 2 and is mounted in trackway 10 on a press bed 11. A pair ofupper and lower hydraulic cylinders 12 are fixed to the press bed 11 andconnected to structure 9 for limited axial movement with respect to dienib 6.

A die holder 13 is mounted on the press bed 11 with the die nib 6suitably disposed within la suitable recess immediately adjacent -thedischarge end of the cylinder 2 opposite from the ram 5, An enlargedpassageway in the die holder 13 extends outwardly from the smallcylindrical die opening in die nib 6 and directs the extruded metal intothe runout tube assembly 7.

A suitable lubricant 14 covers the internal surface of the cylinder 2fand the opening in the die nib 6 to facilitate extrusion of the hotmetal billet 3. The lubricant may be one of the common high temperaturevarieties which usually contain aluminum powder of flakes, graphiteflakes, and a minerol oil vehicle.

A lubricant Isuch as is described in the United States patent to A.Clatot et al. 2,757,138 is a suitable lubricating composition for thehot extr-usion of metals. A lubricant containing about percent graphite,l() percent mineral and 20 percent sodium chloride would besatisfactory. Other lubricants which would be expected to act assatisfactory hot extrusion lubricants are: la combination of about 50percent flake graphite and about 50 percent potassium iodide; acombination of Iabout 33 percent flake graphite, 33 percent sodiumchloride, and 33 percent mineral oil; and a lubricant containing acombination of about 10 percent sawdust, 60 percent ilake graphite, 23percent carbon black, 3 percent Mn02,1and 4 percent linseed oil as isdescribed and used in British Patent 712,007.

As the hot billet 3 is extruded youtwardly through the die nib 6, theworking of the metal results in a further incre-ase in the temperaturethereof. Further, portions of the lubricant 14 Iare volatilized orvaporized and are carried along with the extruded wire 4 into the runouttube assembly 7, These substances react undesirably with the surface ofthe extruded wire 4 to form a hard brittle multiphase carbon coating.The runout tube assembly 7 of the present invention is constructed toprevent the formation of such coatings.

In the illustrated embodiment of the invention, the runout tube assembly7 includes a guide tube 15 mounted in axial alignment with the enlargedpassageway in the die holder 13 and extending axially outwardlytherefrom. A swing tube 16 is releasably secured extending outwardlyfrom the guide tube 15 and is pivotally secured at the outer end to arunout tube 17 which carries the extruded wire and deposits it upon therunout track 8.

Referring particularly to FIG. 2, the guide tube 15 is a tubular membermounted within lan enlarged passageway formed in a die backing andsupporting structure including a die backing plate 18, a die plate 19and a vertical frame or stool base 20 all of which are carried by thepress bed 11.

The guide tube 15 includes a shear tip 21 secured to the forwardmost endof the guide tube 15 by a threaded neck 22 which threads into acorrespondingly threaded portion of the innermost end of the tube 15. Alock washer 23 is threaded onto the neck 22 immediately adjacent the endof the tube 15 to securely lock the shear tip 21 in place. The diameterof the shear tip 21 is substantially the same las the passageway in thedie backing plate 18 and serves to seal the inner surface of the guidetube 15 and to concentrically support the corresponding end of the guidetube 15 within the passageway. The guide tube passageway in stool base20 is enlarged and defines a 1ocating shoulder 24 with the immediatelyadjacent face of the die plate 19. Three locating bars 25 areequicircumferentially spaced about and welded or otherwise secured tothe guide tube 15 as by welds 26 and the outer ends are joined bylocating rings 27, as most clearly shown in FIG. 5. The locating bars 25and rings 27 are positioned axially on the guide tube 15 to abut thelocating shoulder 24 and locate the end of the sheartip 21 in the planeof the face of the die backing plate 1S immediately adjacent the dieholder 13. A tubular ycoupling -member 28 is telescoped over the outerend of the tube 15 and secured thereto as by a circumferential weld 29at the junction of the tube and the end face of the coupling member. Theouter diameter of the coupling member 28 corresponds to the diameter ofthe passageway in the stool base 20 and the coupling member 28 projectsinto this passageway to simultaneously seal the corresponding ends ofthe passageway Vand coaxially support the corresponding end of the guidetube 15.

The guide tube 15 is provided with a plurality of longitudinally spacedsets of three equicircumferentially distributed radial passages 30 whichestablish fluid communication between the interior of the `guide tube 15and the passageways in the plates 18 and 19 and stool base 20. A gasinlet opening 31 is provided in the stool base 20 and connected by gasconduit 32 to a source of a suitable gas, such as air, under a selectedpressure.

As the billet is extruded through the die nib 6, the wire product 4often reaches a temperature near 240()o F. At this temperature, the ironcontent of the billet may absorb about of carbon. Therefore, if carbonin a combinable form occurs in guide tube 15, it may penetrate thesurface of wire 4. The carbon penetrating the wire will initiallyestablish la saturated solution with the iron. As the wire containing asaturated iron-carbon solution cools to a temperature of about '2065 to2085" F., cementite begins to crystallize and separate from thesolution. Ledeburite, a eutectic containing about 4.3% of carbon, beginsto form as the wire cools through this temperature range. As the coolingof the wire rather rapidly progresses, the carbon is retained by thewire in the combined form of austenite, cementite and ledeburte andresults in a hard brittle wire product which is subject to transversecracking and is commercially unsuitable, particularly for cold drawing.

By continuously introducing a gas, such as air, into the guide tube 15under a selected pressure and adjacent the downstream end of theextrusion die 6, the carbonaceous constituents of the vaporized portionof the lubricant, which pass into the guide tube with the extrudedmetal, may be rapidly and continuously purged from the guide tube andthe zone where the temperature of the wire is at a level which permitsthe penetration of carbon into the surface thereof. While, for economicreasons, the gaseous medium generally employed is air, it is believedthat the oxidizing constituents of air augment the flushing and dilutingeffect of the air being injected into the guide tube. These oxidizingconstituents serve to oxidize the carbonaceous elements occurring inguide tube 15 thereby preventing their penetration into the extrudedmember where they may combine with the iron found therein. Therefore,gaseous media, other than air, which include oxidizers would be expectedto render satisfactory noncarburizing results when injected into theguide tube.

The guide tube 15 is of a length which allows all or substantially allof the carburizing constituents present in guide tube 15 to be renderedineffective by being driven off and diluted by the air flow within theguide tube. The extruded wire 4 leaving the guide tube 15 is generallyreduced in temperature to a point below which carbon is insoluble iniron and is therefore not subject to further earburization. The balanceof the runout tube assembly 7 and the runout track 8, therefore, neednot be provided with any special air flushing or decarburizing gaseousmedium.

The guide tube 15 is releasably clamped in place by the swing tube 16which is releasably connected to the outer end of the coupling member 28of the guide tube 15 by a spring loaded coupling assembly 33.

Referring particularly to FIGS. 2-4, the coupling member 28 is providedwith an outwardly extending reduced tubular portion 34. A tubularcoupling 35 is slidably disposed on the reduced tubular portion 34 andabuts a shoulder 36 defined by the reduced portion 34. The opposite endof the tubular coupling 35 is slidably disposed on the adjacent end ofthe swing tube 16. An axial slot 37 is provided in the coupling 35 andmates with a radial pin 38 secured to the outer wall of the swing tube16. The slot 37 and pin 38 allows limited axial movement of the coupling35 on swing tube 16 while interconnecting the two members. A coil spring39 encircles the swing tube 16 between the end of the coupling 35 and ashoulder 40 formed on the tube 16. The coil spring 39 continuouslybiases the coupling 35 onto the coupling member 28 to releasablyinterconnect the swing tube 16 to the guide tube 15. To disconnect theswing tube 16 from the coupling member 28 of the guide tube 15, it ismerely necessary to slide the coupling 35 axially onto the swing tube 16until the end of the coupling 35 clears the corresponding end of thecoupling member 28.

The opposite end of the swing tube 16 is pivotally secured to the runouttube 17 in the following manner. A clamp member 41 includes a splitclamp portion 42 rigidly secured to the outer end of the swing tube 16and a similar split clamp portion 43 releasably secured to the adjacentend of the runout tube 17. Small pivot pins 44 and 45 are secured to thesplit clamp portion 43 on opposite sides of a runout tube 17. The innerends of the pivot pins 44 and 45 bear on the adjacent portion of therunout tube 17, as shown in FIG. 2, for swinging movement of the member41 and the attached swing tube 16 about the vertical axis through pins44 and 45.

To remove the guide tube 15, the coupling 35 is axially slid onto theswing tube 16 against the bias of spring 39 until the outer end of thecoupling 35 clears the coupling member 28. The swing tube 16 is thenpivoted about the axis of pins 44 and 45 to the dotted line position ofFIG. 3. The guide tube 15 can then be withdrawn from the correspondingpassageways.

The runout tube 17 and runout track 8 may be any desired or suitableconstruction and no further description thereof is deemed necessary tothe complete understanding of the invention.

'I'he operation of the present invention is summarized as follows.

The ram is withdrawn from the cylinder 2. The surfaces of the cylinder 2and die nib 6 subject to contact with a billet are provided with alubricant 14. A heated billet 3 of low carbon steel or any othersuitable metal is disposed within the cylinder 2.

Ram 5 is then moved into cylinder 2 to force the billet 3 through thedie nib 6 and by extrusion form an elongated wire 4 having a continuouslength many times that of the billet 3.

In accordance with the present invention, simultaneously with theinitiating of the extrusion process, air is fed into guide tube 15 fromline 32. The air enters the guide 15 through the many radial passages 30and moves outwardly through the guide tube 15 and swing tube 16 tomaintain a non-carburizing atmosphere about the hot extruded wire 4. Theair in the tube 15, which is heated during operation, prevents theformation of appreciable high carbon coatings on the surface of the wire4.

The present invention thus provides a method and apparatus of extrudingmetal members Without the formation of undesirable carbide coatingsthereupon and is particularly adapted for extrusion of carbon and carbonalloy steel into wire-like elements which are to be subsequently colddrawn.

Various modes of carrying out the invention are contemplated as`V beingwithin the scope of the following claims particularly pointing out anddistinctly claiming the subject matter which is regarded as theinvention.

I claim:

1. In a process of extruding material from a die opening in a heatedcondition, the improvement comprising the steps of extruding the heatedmaterial through a lubricated die and saturating the zone adjacent thedie opening with an oxidizing agent to prevent carburization of theextruded material.

2. A method of extruding a heated material subject to carburizationcomprising expressing the material from a die, establishing a highermaterial temperature adjacent the downstream side of the die than theupstream side of the die, and introducing an oxidizing agent into thezone adjacent the downstream side of the die as a continuously flowinggas to prevent carburization of the extruded matrrialg '3. In a methodof extruding a material from a group comprising carbon steel, alloysteel, carbon metals and nickel alloy, the steps of heating thematerial, extruding the heated material from a die orifice, heating thezone adjacent the die orifice and ilushing the heated zone with anoxidizing agent to prevent carburization of the heated material.

4. A method of hot extruding a billet of material subject tocarburization comprising heating the billet, lubricating the billet witha carbon-bearing lubricant, expressing the billet from an extrusion die,and flushing the zone adjacent the downstream side of the die with anoxidizing gas to prevent carburization of the extruded material.

5. A method of .hot extruding a billet of material subject tocarburization comprising heating the billet, lubricating the billet witha carbon-bearing lubricant, expressing the billet from an extrusion die,and flushing the zone adjacent the downstream side of the die with airto prevent carburization of the extruded material.

6. The method of hot extruding a billet of material subject tocarburization comprising the steps of heating the billet, lubricatingthe billet with a carbon bearing lubricant, expressing the billet froman extrusion die, heating the zone immediately adjacent the dischargeside of the extrusion die to maintain the carbon constituents of thelubricant in a volatile condition, and flushing the zone adjacent thedownstream side of the die with an oxidizing gas to preventcarburization of the extruded material.

References Cited UNITED STATES PATENTS 2,097,502 11/1937 Southgate207-10.11 3,096,881 7/-1963 Tombaugh 7?.-364 3,120,305 2/ 1964 Linnerz723 64 3,160,951 12/1964 Markert et al. 72-3 64 FOREIGN PATENTS 210,8682/ 1924 Great Britain.

691,875 5/ 195 3 Great Britain.

777,845 6/ 1957 Great Britain.

OTHER REFERENCES Metals Handbook, 1948 ed., published by: The AmericanSociety for Metals, Cleveland (page 5, definition of decarburizationrelied upon).

CHARLES W. LANHAM, Primary Examiner. E, COMBS, Assistant Examiner,

1. IN A PROCESS OF EXTRUDING MATERIAL FROM A DIE OPEN ING IN A HEATEDCONDITION, THE IMPROVEMENT COMPRISING THE STEPS OF EXTRUDING THE HEATEDMATERIAL THROUGH A LUBRICATED DIE AND SATURATING THE ZPNE ADJACENT THEDIE OPENING WITH AN OXIDIZING AGENT TO PREVENT CARBURIZATION OF THEEXTRUDED MATERIAL.